소프티어

#include <stdio.h>
#include <stdlib.h>

int comp_func(const void **p1, const void **p2)
{
  int* arr1 = *(int**)p1;
  int* arr2 = *(int**)p2;
  int price1 = arr1[1];
  int price2 = arr2[1];
  
  if(price1 < price2) return 1;
  else if(price1 > price2) return -1;
  else return 0;
}

int main(void)
{
  int BagWeight = 0;
  int IronTypeNum = 0;

  scanf("%d %d", &BagWeight, &IronTypeNum);
  int** Arry = (int**)malloc(sizeof(int*)*IronTypeNum);
    
  for(int i=0; i<IronTypeNum; i++)
  {
    Arry[i] = (int*)malloc(sizeof(int)*2);
    scanf("%d %d", &Arry[i][0], &Arry[i][1]);
  }
  
  //Quick sort based on the price per 1kg
  qsort(Arry, IronTypeNum, sizeof(int**), comp_func);

  /*for(int i=0; i<IronTypeNum; i++)
  {
     printf("%d, %d\n", Arry[i][0], Arry[i][1]);
  }*/
 
  int answer = 0;

  for(int i=0; i<IronTypeNum; i++)
  {
    if((BagWeight - Arry[i][0]) >= 0) answer += (Arry[i][0]*Arry[i][1]);
    else
    {
      answer+= (BagWeight*Arry[i][1]);
      break;
    }

    BagWeight -= Arry[i][0];
  }

  printf("%d", answer);
  return 0;
}